1. Technical Field
The invention relates generally to broadcast signal receivers and, more specifically, to a system for detecting broadcast signals having a low or negative signal-to-noise ratio.
2. Description of the Prior Art
It is often desirable to detect a signal having a low or even negative signal-to-noise ratio. For example, a radio beacon on a downed aircraft may provide a faint radio signal that is overshadowed by background radio noise. Similarly, a signal from a communication device such as a cellular phone might be masked by noise at the edge of a specified coverage area. Such signals are particularly difficult to detect or analyze, as most attempts to amplify the weak signal will also amplify the accompanying noise. If the signals can be detect amid all of the noise, however, it may be possible to retrieve the signal from a buffer or determine the location of the source.
In other applications, a signal is made intentionally weak to avoid interception. For example, in a low probably of intercept (LPI) radar system, the signal is intentionally maintained at low power in an attempt to mask the signal with background noise. Even when general characteristics of the radar signal are known, conventional radar detectors cannot detect or analyze this weak signal to determine the position of the radar. Accordingly, it can be difficult to neutralize an LPI radar unless the radar transceiver is located by other, less dependable means.